Physiologic markers indicating the progression of a disease are crucial to the proper modulation of a patient's treatment. Doctors use such markers both as a predictor of future disease course and as a feedback mechanism for optimizing treatment. Unfortunately, many such markers are cost prohibitive and/or are not amenable to repetitive or continuous use in patients away from a medical setting such as a hospital. Doctors often are forced to treat patients based only on symptoms presented at the time of patient-physician interaction. However many predictive symptoms only occur in the later stages of a disease and/or can be subjective in nature. Therefore, the progression of a patient's true condition and a systematic objective prediction of the future disease course frequently remain largely unknown. Early markers that precede the appearance of late-stage symptoms are needed. The earlier a doctor is aware of a patient's condition, the earlier he/she can intervene, possibly slowing or reversing the progression of the disease.
For example, congestive heart failure (CHF) is a chronic and progressive condition. Optimal management of patients with CHF requires close monitoring because CHF patient's clinical status can deteriorate rapidly and suddenly. Therefore, there is continuing need and interest in developing better methods and devices to manage CHF and other chronic diseases.